Automatic vehicle exterior light control systems provide a significant convenience function for drivers by alleviating the burden of manually switching between high and low beam headlights in response to changing traffic conditions. It is known that drivers, on average, do not utilize their high beam headlights as often as is appropriate. High beam headlights can provide from two to four, or more, times the visibility distance at night as compared to low beam headlights. Thereby, a driver of a controlled vehicle is enabled to detect an obstacle or pedestrian at night earlier than otherwise would be the case. There is a safety benefit during night time driving introduced by automating the beam switching task and increasing the average utilization of high beam headlights.
Known systems designed to automatically control vehicle exterior lights utilize a forward looking digital imaging system to acquire images of the scene generally in front of the controlled vehicle, to analyze the images and to detect headlights of oncoming vehicles and taillights of leading vehicles. If ambient lighting conditions are low enough to warrant high beam headlight usage and no oncoming or leading vehicles are detected, high beam headlights are automatically activated. When other traffic is detected within the range where drivers of the other vehicles would experience glare induced by the high beam headlights of the controlled vehicle, the high beam headlights of the controlled vehicle are automatically reduced in intensity, the aim redirected, inhibited from operation or a combination thereof. In addition, or as an alternative, to controlling high beam headlights, automatic vehicle exterior control systems may be adapted to control a variety of lighting technologies, including the intensity of at least one low beam headlight, the aim of at least one low beam headlight, bending light, motorway lighting, town lighting, fog light, taillight or any other vehicle illumination device. It should be understood that wherein the disclosure below specifically mentions the control of high beam headlights, or the inhibiting of automatic high beam headlight control, those methods may be also applied to the control of a variety of exterior lighting technologies including, but not limited to, those listed above.
A problem with known systems occurs at various times when, due to a variety of factors, high beam headlight operation is not desired even when there are no oncoming or leading vehicles. Examples of such situations include poor weather such as fog, a snow storm or when the light from high beam headlights of the controlled vehicle reflects off of atmospheric conditions of interest and distracts the driver of the controlled vehicle. Certain atmospheric conditions also attenuate light rays coming from other vehicles making it more difficult for an imaging system to detect them at sufficient distance. Another condition when high beam headlights are generally not desired is when driving in towns. In some European countries high beam headlight use is prohibited in towns, even if there are no oncoming or leading vehicles.
Another problem associated with use of an imaging system to automatically control vehicle exterior lights occurs when the view of the associated image sensor may be blocked or obstructed by objects or contamination in front of the image sensor. Preferably, the imaging system is integrated into the rearview mirror assembly of the controlled vehicle such that the image sensor is positioned behind the windshield in a region where the associated windshield wipers clean. However, even in this configuration, the possibility exists that ice or other contaminates cannot be removed by the wipers and will still block the image sensor. In these cases, the image sensor may not be able to sense the lights from oncoming or leading vehicles and the system will incorrectly conclude that there are no vehicles present and activate the high beam headlights, causing glare to drivers of other vehicles. These situations require the driver of the controlled vehicle to intervene and switch the automatic system off which may lead to dissatisfaction with the automatic feature and reduced confidence in the automatic vehicle exterior light control system. Thus, it is advantageous to automatically detect situations where the automatic high beam control system cannot perform satisfactorily and automatically disable the feature and revert to a fail-safe low beam condition. In these situations manual control is typically still provided allowing the driver to determine the desired exterior light state when the automatic system is unable to perform.
What are needed are automatic vehicle exterior light control systems that provide improved features to detect related operational environments. Systems configured to automatically respond to detected operational environments are also needed.